首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   631篇
  免费   22篇
  国内免费   1篇
林业   62篇
农学   60篇
基础科学   9篇
  159篇
综合类   36篇
农作物   50篇
水产渔业   73篇
畜牧兽医   111篇
园艺   6篇
植物保护   88篇
  2023年   14篇
  2022年   11篇
  2021年   12篇
  2020年   15篇
  2019年   24篇
  2018年   23篇
  2017年   23篇
  2016年   29篇
  2015年   9篇
  2014年   26篇
  2013年   71篇
  2012年   36篇
  2011年   34篇
  2010年   25篇
  2009年   24篇
  2008年   33篇
  2007年   24篇
  2006年   25篇
  2005年   18篇
  2004年   17篇
  2003年   15篇
  2002年   12篇
  2001年   21篇
  2000年   7篇
  1999年   13篇
  1998年   6篇
  1997年   2篇
  1995年   2篇
  1994年   4篇
  1993年   4篇
  1992年   4篇
  1991年   2篇
  1990年   5篇
  1989年   5篇
  1988年   7篇
  1987年   5篇
  1986年   4篇
  1985年   5篇
  1984年   2篇
  1983年   6篇
  1982年   5篇
  1981年   3篇
  1980年   5篇
  1979年   2篇
  1976年   2篇
  1974年   2篇
  1971年   2篇
  1967年   1篇
  1966年   3篇
  1954年   1篇
排序方式: 共有654条查询结果,搜索用时 46 毫秒
101.
102.
The present study describes the role of different exogenous hormones on morphology and plumbagin production in Plumbago indica hairy roots. It was also aimed to conserve elite root clones via synthetic seed technology. Insertion of rolB gene in transformed roots was confirmed by polymerase chain reaction followed by southern blot analysis. Hairy roots were treated with single or in combination of different phytohormones viz. IAA, IBA, 2, 4-D, NAA, BAP, GA3 and ABA. Cultures incubated with GA3 (0.5 mg l−1) yielded highest root growth due to formation of profuse lateral branching while NAA (0.5 mg l−1) treatment caused highest plumbagin accumulation. Cultures incubated with 2, 4-D exhibited highest inhibitory effect in terms of both root growth and plumbagin production. All phytohormones were found to be effective at lower concentration. In combinatorial study, GA3 + NAA (0.5 mg l−1, each) was found optimum for root biomass and plumbagin production at earlier stage of culture. Different combinations of auxins and BAP induced different morphologies ranging from reduction of lateral branching to rapid disorganization of root matrix. The combinations of ABA and selected auxins were not found promising at any of selected concentration. Based on the effect of exogenous hormones on hairy root culture, elite root clones were selected and encapsulated with sodium alginate matrix. Uniform shaped alginate coated synthetic seeds were conserved up to 6 months exhibited high regeneration potential without disturbing plumbagin content.  相似文献   
103.
A study was undertaken to investigate the remedial effect of some soil amendments (farmyard manure (FYM), press mud compost (PMC), cereal straw (CS) at 5 t ha?1 and fresh cow dung slurry (FCD) @ 0.5 t ha?1) on dissipation kinetics of imidacloprid and sulfosulfuron under laboratory conditions. Incorporation of CS or FCD was found to be most effective in degrading both the pesticides at faster rates. Dissipation of both the pesticides could be well accounted by two component (1 + 1) first order kinetics. The computed values of parameters revealed that use of organic amendments increased the dissipated fraction of imidacloprid and sulfosulfuron. Incorporation of CS or FCD in soil maintained relatively higher dissipation rate constants for both faster and slower dissipation processes of pesticides in comparison to control. Hence, eco-friendly practices of CS or FCD incorporation as soil amendment in soil can play a vital role in preventing soil and water pollution.  相似文献   
104.
The steam explosion (SE) pretreatment associated with the organosolv process was investigated to produce dissolving pulp from eucalyptus. Prehydrolysis Kraft (PHK) pulping was also done to produce viscose and acetate grade pulps as reference. The organosolv pulps were delignified in two steps with sodium chlorite. Viscose and acetate grade PHK pulps were bleached by OD0(EH)D1P and OD0(EP)D1PCCE sequences, respectively. Dilute acid-catalyzed (with acid addition) SE pretreatment dissolved more xylan than auto-catalyzed (no acid addition) SE pretreatment. Steam-exploded unbleached organosolv pulps showed lower residual lignin content and screened yield than unbleached organosolv pulps without SE pretreatment. Steam explosion pretreatment helped to decrease lignin content and damaged fiber length of unbleached organosolv pulps. The 1.0% H2SO4 organosolv pulp (organosolv dissolving pulp at bioconversion conditions) showed the highest reactivity. Even showing low viscosity for some applications, in general, the organosolv dissolving pulps produced in this study can be used for making lyocell fibers.  相似文献   
105.
106.
Healthy wheat kernels and wheat kernels damaged by the feeding of the insects: rice weevil (Sitophilus oryzae), lesser grain borer (Rhyzopertha dominica), rusty grain beetle (Cryptolestes ferrugineus), and red flour beetle (Tribolium castaneum) were scanned using a near-infrared (NIR) hyperspecrtal imaging system (700-1100 nm wavelength range) and a colour imaging system. Dimensionality of hyperspectral data was reduced and statistical and histogram features were extracted from NIR images of significant wavelengths and given as input to three statistical discriminant classifiers (linear, quadratic, and Mahalanobis) and a back propagation neural network (BPNN) classifier. A total of 230 features (colour, textural, and morphological) were extracted from the colour images and the most contributing features were selected and used as input to the statistical and BPNN classifiers. The quadratic discriminant analysis (QDA) classifier gave the highest accuracy and correctly identified 96.4% healthy and 91.0-100.0% insect-damaged wheat kernels using the top 10 features from 230 colour image features combined with hyperspectral image features.  相似文献   
107.
Objectives: To report the repair of tibial diaphyseal fractures in 2 calves using a circular external skeletal fixator (CEF). Study Design: Clinical report. Animals: Crossbred calves (n=2; age: 6 months; weight: 55 and 60 kg). Methods: Mid‐diaphyseal tibial fractures were repaired by the use of a 4‐ring CEF (made of aluminum rings with 2 mm K‐wires) alone in 1 calf and in combination with hemicerclage wiring in 1 calf. Results: Both calves had good weight bearing with moderate lameness postoperatively. Fracture healing occurred by day 60 in 1 calf and by day 30 in calf 2. The CEF was well maintained and tolerated by both calves through fracture healing. Joint mobility and limb usage improved gradually after CEF removal. Conclusions: CEF provided a stable fixation of tibial fractures and healing within 60 days and functional recovery within 90 days. Clinical Relevance: CEF can be safely and successfully used for the management of selected tibial fractures in calves.  相似文献   
108.
The aim of this study was to determine the genetics of polymorph systems of Transferrin in Garole sheep breed. The present study was conducted on 95 adult Garole sheep comprising 52 ewes and 43 rams, maintained at Sheep and Goat Breeding Farm of West Bengal University of Animal and Fishery Sciences, West Bengal, during the period from April–September, 2009. The polymorphism of transferrin was determined through SDS-Polyacrylamide gel electrophoresis technique. It was found that the transferrin type was controlled by five codominant alleles (TfA, TfB, TfC TfD and TfE) in Garole sheep. These five alleles, because of co-dominant nature of inheritance, determined the occurrence of nine transferrin genotypes in the analyzed flock. Four (TfAA, TfBB, TfCC and TfDD) of these were homozygous and the remaining five (TfAD, TfBC, TfBD, TfCD and TfDE) heterozygous. It was found that the TfDD genotype (0.263) was predominant while TfDE genotype (0.042) was least common in the analyzed flock. Frequencies of other genotypes were as: TfCD(0.242), TfBD(0.126), TfCC(0.084), TfBB(0.074), TfAA(0.063), TfAD and TfBC (0.053 for each genotype ) in whole population. From the result it was found that in whole population combined, the heterozygotic genotypic frequency (0.516) was more than that of homozygotic genotypic frequency (0.484). Considerable variations were recognized in the frequencies of transferrin alleles. In the whole population frequencies of transferrin alleles were found to be TfA = 0.089, TfB = 0.163, TfC = 0.232, TfD = 0.495 and TfE = 0.021. Transferrin system has shown an absence of genetic equilibrium among the analyzed herd (χ2 value = 51.31). In conclusion, there were polymorphism in Transferrin types and the presence of differences among the frequencies of the five alleles by categories could be a source of genetic variation in Garole sheep.  相似文献   
109.
The experiment was conducted with three biofloc treatments and one control in triplicate in 500 L capacity indoor tanks. Biofloc tanks, filled with 350 L of water, were fed with sugarcane molasses (BFTS), tapioca flour (BFTT), wheat flour (BFTW) and clean water as control without biofloc and allowed to stand for 30 days. The postlarvae of Litopenaeus vannamei (Boone, 1931) with an Average body weight of 0.15 ± 0.02 g were stocked at the rate of 130 PL m?2 and cultured for a period of 60 days fed with pelleted feed at the rate of 1.5% of biomass. The total suspended solids (TSS) level was maintained at around 500 mg L?1 in BFT tanks. The addition of carbohydrate significantly reduced the total ammonia‐N (TAN), nitrite‐N and nitrate‐N in water and it significantly increased the total heterotrophic bacteria (THB) population in the biofloc treatments. There was a significant difference in the final average body weight (8.49 ± 0.09 g) in the wheat flour treatment (BFTW) than those treatment and control group of the shrimp. Survival of the shrimps was not affected by the treatments and ranged between 82.02% and 90.3%. The proximate and chemical composition of biofloc and proximate composition of the shrimp was significantly different between the biofloc treatments and control. Tintinids, ciliates, copepods, cyanobacteria and nematodes were identified in all the biofloc treatments, nematodes being the most dominant group of organisms in the biofloc. It could be concluded that the use of wheat flour (BFTW) effectively enhanced the biofloc production and contributed towards better water quality which resulted in higher production of shrimp.  相似文献   
110.
Management of Pests and pesticides: Farmers’ Perceptions and Practices. Editors Joyce Tait and Banpot Napompeth, Boulder, Col.: Westview Press 1987. ISBN 0–8133–7174–0, £33 paperback.

Termites in Buildings. Their Biology and Control. R. Edwards and A. Mill. Rentokil Library, 1987, ISBN 0906 5640 69 £24–50.

Pesticide Science and Biotechnology. Proceedings of the Sixth International Congress of Pesticide Chemistry. Ottawa, Canada, 10–15 August 1986. Edited by R. Greenhalgh and T. R. Roberts. IUPAC/Blackwell Scientific Publications, 1987 (602 pp + xiii).

Breeding for Resistance to Diseases and Insect Pests. By D. P. Singh. 222 pp + xi. ISBN 0 387 16970 9. Springer Verlag. 1986. Price $7900.

Pest Control Safe for Bees: A Manual and Directory for the Tropics and Subtropics. By M. Adey, P. Walker and P. T. Walker, 1986. International Bee Research Association, London. Price £12–20.

The Cocoa Pod Borer: An Introduction and Abstracts. Compiled by Lim Guan Soon et al. Malaysian Plant Protection Society, Box 12351 Kuala Lumpur. 1987. 103 pp. ISBN 967–9942–07–4.

Pentachlorophenol. Environmental Health Criteria, No. 71, World Health Organization, Geneva, 1987. 236 pages, ISBN 92 4 154271 3. Price: Sw.fr. 18—/US$1080.

Ecology and Control of Perennial Weeds in Latin America. FAO Plant Production and Protection Paper No. 4. Food and Agriculture Organization, Rome. 1986, 339 pp. ISBN 92–5–102446–4.

Proceedings of the 2nd International Workshop on Leaf hoppers and Planthoppers of Economic Importance. Edited by M. R. Wilson and L. R. Nault. CAB International Institute of Entomology. 1987. 368 pp. ISBN 0–900301–03–1.

Breeding for Durable Resistance in Perennial Crops. FAO Plant Production and Protection Paper No. 70 (1986). 130 pp.

Ascochyta Blight Resistance in Chickpea. Proceedings of a training course, PARC/ICARDA, 3–10 March, 1984, Islamabad, Pakistan. ICARDA, 1986, 123 pp.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号